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Formation and Evolution of Dark Matter Halos (II．Formation of the Large-Scale Structure of the Universe) ver.2

This video focuses on the formation and evolution of the dark matter distribution from the early Universe to the present. In our Universe, small density fluctuations in the dark matter form into small clumps (called dark matter halos) through the effects of gravity. Some of these merge together to form larger halos. Within these halos, gas condenses and forms galaxies. Hundreds of galaxies gravitationally bound to each other form galaxy clusters.Galaxies and clusters are distributed in an interconnected web pattern. Such structures are called the large-scale structure of the Universe.
This video is based on a simulation taken from a suite of simulations named ν²GC (New Numerical Galaxy Catalog) . Small density fluctuations in the early Universe are represented by 8.6 billion dark matter particles. The gravitational interactions between these particles were calculated by the supercomputer ATERUI and the evolution to the present epoch was simulated. By calculating the evolution of the ingredients for stars and galaxies (called baryons) with a semi-analytic model, we can predict the distribution, evolution, and statistical properties of the galaxies and active galactic nuclei which exist in the dark matter halos. With this simulation suite, for the first time we will be able to compare simulation predictions to forthcoming state-of-the-art wide-field observations (e.g. the Subaru Telescope/HSC).

	Dark matter is distributed almost uniformly in the early Universe, but small density fluctuations exist. Regions with higher density gather surrounding matter as a result of gravitational interactions and increase their density further to form halos. The initial dark matter distribution is based on state-of-the-art observational results obtained by the Planck Mission.
	Many small dark matter halos are formed. Halos repeatedly merge together to form larger halos. This simulation only follows the evolution of the dark matter distribution. In the real Universe, ingredients like hydrogen and helium for the first stars and galaxies are concentrated in the centers of the halos.
	This stage corresponds to the present Universe. Many large halos may host clusters or galaxies, forming large-scale structures.
	Web structures connecting the groups of halos can be seen. This is the large-scale structure of the Universe.
	The largest halo in this simulation is displayed. The mass is about 5x1014 solar masses, corresponds to a galactic cluster. Many small halos wander around the central halo. These are called sub-halos and thought to host member galaxies of the cluster.

Details of numerical simulation

Purpose	Studying the distribution, evolution and statistical properties of dark matter, galaxies and active galactic nuclei.
Model	LCDM
Model	Particles： 2048³(=8,589,934,592) dark matter particles
Computer	Cray XC30 "ATERUI" (CfCA, NAOJ)
Time scale	~13.8 billion years
Spatial scale	~210Mpc
Researcher	Tomoaki Ishiyama (Chiba University)
Reference	“The ν²GC Simulations : Quantifying the Dark Side of the Universe in the Planck Cosmology”, Ishiyama, T., Enoki, M., Kobayashi, M.A.R., Makiya, R., Nagashima, M., Oogi, T. arXiv:1412:2860, accepted by Publications of the Astronomical Society of Japan The ν²GC Simulations (Database website)

The results of the calculation visualized in this movie were supported in part by MEXT SPIRE Field 5 and JICFuS.

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Detail of visualization

In this movie, the number of dark matter particles has been reduced from 8.6 billion to 90 million. The 3D dome master movie was made with a technique which enables stereoscopic viewing in almost all directions. This video was produced with the 3DCG software “Maya”.
In addition, 360 degree panoramic content is also produced simultaneously. Viewing this format with a head mounted display (HMD) provides a realistic experience.